[rikf]

It should be possible to determine fake from real accounts using various statistics like number of likes per account average number of time between likes etc etc, with all the brainpower at Facebook I am surprised they haven't significantly mitigated this problem. This is not a problem that can ever be completely solved as its a typical arms race between good and evil but i am surprised at how badly Facebook appears to be doing as others have noted perhaps its because it in there best interest or maybe its just more visible on Facebook then it would be on google addwords or similar.

[fblp]

Yes, we wrote about this at http://fbk.io/stopfakelikestoday. In short Facebook could compare behaviour as you suggested (they've got a whole bunch of data scientists). An even more robust way would be making their phone number verification more thorough.

[jonknee]

It could be devastating to their business. Facebook is in a tough spot, they are done or nearly done growing in the US and much of the developed world. Most of this fraud seems to happen in emerging markets, the exact same ones much of their "growth" is coming from. If growth numbers go negative or even flat Wall Street would run away from FB faster than you can cancel an advertising campaign.